Ideas
I'm able to upload and download lots from the gallery/library, but the error message still pops up when saving the lots, I wait until the upload window behind the message closes and then click "x" on the error message not on "ok" to close it, and the lots are uploaded. I find it preposterous that people have to find workarounds to the issues EA has to fix, they're more concerned about making a survey about insoi instead of fixing their own game.
They made a survey about InZoi?! What a slap to simmers. My issue with saving to my gallery has "evolved" also to be the same as you say, now I wait for the green window. Saving is a fundamental part of the game. EA acting like they are puzzled about how they broke it is another insult. I'm on Mac, but here's some info about Inzoi for EA. If they treat their customer base with respect they'll earm customers away from TS4.